Curious about how a 3D printer really works? Now you can see one printing everything from Lego-style bricks to a model Eiffel Tower (plus a failed try at a human skull).

Computerworld was able to try out the Afinia H-Series 3D Printer, which uses fused deposition modeling (FDM), an additive manufacturing process. Melted thermoplastics are extruded from a hair-thin hole in a nozzle and set down on a platform, layer by layer, building objects from the ground up.

To build an object, a computer-aided design (CAD) drawing is first sliced into layers and sent as virtual pages to a processer in the printer that controls the robotic mechanism. Even simple objects can take hours to build, but the advantage over traditional manufacturing (and food production) is it requires no tooling -- and prototype changes can be made on the fly.

Here are seven high-speed videos demonstrating the technology, including two other methods: selective laser sintering and stereolithography.

The model of the Empire State Building was one of the more successful 3D print jobs we were able to build with the Afinia H-Series 3D Printer. The model’s design was simple and straightforward, which meant less scaffolding support material was needed around it than with most of the other models. As a result, this one was cleaner and easier to finish off.

The Eiffel Tower is a good example of how scaffolding material can ruin a 3D printed object. The model tower, intricate and delicate in design, broke easily when the scaffolding support material was removed with an X-Acto blade and snips. (At the end of the video you'll see that the tower's spire has snapped off.) Still, the Eiffel Tower is an example of how precise 3D printing can be.

This model of a Porsche 911 came out relatively well. It took more than three hours to build, not atypical for even small objects. It also had some great details, such as side mirrors and a license plate.

The 3D printed Lego-style bricks were a lot of fun to build. Because they were relatively small, multiple bricks could be printed on the platform at the same time. They also printed quickly; these took less than two hours to make. This video shows how wheels and axles were formed.

Not all print jobs were successful. During this attempt to print this human skull, the printer was unable to translate the CAD drawing into an object and went awry about a quarter of the way through the job.

What you’ll see to the left of the screen is a bird’s nest of extruded thermoplastic -- the result of trying to build supports for the rear of the skull. This was not the only failed 3D print job. Several of them ended unsuccessfully.

Selective laser sintering (SLS) is a 3D printing technique that uses lasers to melt successive layers of powdered polymers. Unlike fused deposition modeling, where polymers are melted and extruded from a hair-thin hole in a nozzle layer by layer, SLS 3D printers melt layers in a bed of powder.

As each layer is melted, an additional layer of powder from a cartridge is added atop the preceding layer. Each layer is fused to the layer beneath it as it melts. As with all 3D printing, CAD software directs the robotic laser mechanism as it builds the object.

Stereolithography 3D printing is a technology in which a laser hardens a photo-curable resin. A mechanical positioning system directs a laser onto a tray of liquid resin and traces out each layer of an object.

As the laser outlines the shape of the object, it heats and hardens the resin. A platform, either submerged in the resin or positioned above it, is lowered or raised as each layer of the object is built. As the platform moves away from the resin, the hardened material is exposed. While the resin is more expensive than the thermoplastic filament found in most 3D printers today, stereolithography offers higher resolution and smoother surface quality.